Comment 15 for bug 1587065

Prior to the update:

$ virsh domfsfreeze x-freeze; virsh domfsthaw x-freeze
error: Unable to freeze filesystems
error: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to freeze /: Device or resource busy

Thawed 0 filesystem(s)

$ sudo apt install qemu-guest-agent
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  qemu-guest-agent
1 upgraded, 0 newly installed, 0 to remove and 27 not upgraded.
Need to get 132 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu xenial-proposed/universe amd64 qemu-guest-agent amd64 1:2.5+dfsg-5ubuntu10.31 [132 kB]
Fetched 132 kB in 0s (1.161 kB/s)
(Reading database ... 54125 files and directories currently installed.)
Preparing to unpack .../qemu-guest-agent_1%3a2.5+dfsg-5ubuntu10.31_amd64.deb ...
Unpacking qemu-guest-agent (1:2.5+dfsg-5ubuntu10.31) over (1:2.5+dfsg-5ubuntu10.30) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu21.2) ...
Processing triggers for ureadahead (0.100.0-19) ...
Setting up qemu-guest-agent (1:2.5+dfsg-5ubuntu10.31) ...

Retesting the above:
$ virsh domfsfreeze x-freeze; virsh domfsthaw x-freeze
Froze 1 filesystem(s)

Thawed 1 filesystem(s)

Found no other hickups due to the update, setting verified.